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<H1>About notification messages</H1>

<p>HTML Help notification messages are sent from a help window to the window that you specify in an HtmlHelp() call. Use notification messages to track a user's activities in a help window. For example, if you want to invoke an action when a user clicks the <b>Refresh</b> button on the toolbar, you could use the <a href="msg_hhn_track.htm">HHN_TRACK</a> message.

<p>Notification messages occur for the following events:</p>
<ul>
<li>When a user clicks a button on the toolbar or clicks a tab on the Navigation pane of the <a href="wintypes_viewer.htm">HTML Help Viewer</a>, an <a href="msg_hhn_track.htm">HHN_TRACK</a> message is sent that identifies the button or tab that was clicked.</li>

<li>When a user navigates to a topic, an <a href="msg_hhn_navcomplete.htm">HHN_NAVCOMPLETE</a> message is sent that identifies the topic navigated to.</li>

<li>When a help window is created, an <a href="msg_hhn_window_create.htm">HHN_WINDOW_CREATE</a> message is sent that identifies the window being created.</li>
</ul>


<h2>To enable notification message tracking</h2>

<p>HTML Help sends notification messages from help windows that have the following <a href="str_hh_wintype.htm">HH_WINTYPE</a> property settings:</p>
<ul>
<li>The value of <i>hwndCaller</i> must be non zero.</li>
<li>The value of <i>idNotify</i> must be non zero.</li>
<li>A value must be specified for <b>HHWIN_PARAM_PROPERTIES</b> in the <i>fsValidProperties</i> member.</li>
<li>A value must be specified for <b>HHWIN_PROP_TRACKING</b> in the <i>fsWinProperties</i> member.
</li>
</ul>

<h2>To specify the window that will receive notification messages</h2>

<p>Notification messages are sent to the window specified in the <i>hwndCaller</i> parameter of the HtmlHelp() call.</p>

<p>HTML Help notification messages are sent via Windows <b>WM_NOTIFY</b> messages.</p>

<h2>Note</h2>
<ul>
<li>Notification messages are not sent if the value of <i>hwndCaller</i> is the desktop.
</li>
</ul>

<H2>Notification messages quick reference</H2>

<UL>
<LI><a href="msg_HHN_NAVCOMPLETE.htm">HHN_NAVCOMPLETE</a></LI>
<LI><a href="msg_HHN_TRACK.htm">HHN_TRACK</a></LI>
<LI><a href="msg_HHN_WINDOW_CREATE.htm">HHN_WINDOW_CREATE</a></LI>
</UL>

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<td><a href="ov_html_help_api_overview.htm">About the HTML Help API</A>
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